It is common in hallways and entrances in public and commercial buildings, and in offices, to have signs delineating a path to an exit. These signs are generally illuminated with red or green letters and arrows to give building occupants a constant reminder of the location of an exit if an emergency should occur. These signs generally comprise a rectangular enclosure having a mask or stencil that is cut out to provide the desired indicia, for example, the words "exit", "stairs", "restroom" etc. The mask is backed by a translucent colored panel, and generally an incandescent or fluorescent lamp within the enclosure provides the mostly direct light energy that passes through the translucent panel and illuminates only the pattern of indicia for external viewing. This sign may be one sided or two sided.
When the internal incandescent or fluorescent lamps burn out, they must be replaced. This occurs with relative frequency as the exit-type sign is generally in continuous use, 24 hours a day, seven days a week, 8700 hours per year. Incandescent lamps as used in conventional exit signs have a life expectancy on the order of 10,000 hours and fluorescent bulbs have a life expectancy of approximately 20,000 hours. In a larger building where there are many exit signs, and signs leading to exits, as well as other exit-type signs replacement of bulbs is an ongoing task, and an expensive one.
In addition to the high maintenance requirements for conventional incandescent and fluorescent signs, power consumption is a significant factor, especially in large structures where there are many, many signs. The total power consumed by exit signs alone in the U.S.A. is estimated to be in excess of 20 million megawatt-hours per year.
Thus, it would be of great benefit to building owners and the country in general, to reduce the power consumption by a factor of at least 10 or 20 times. As a result of the cumulatively high cost, maintenance of the exit signs is frequently neglected and a sign which is designed to operate with two lamps is frequently left to operate with one lamp or even no lamps for a period of time. Single lamp operations of such signs results in uneven lighting of the indicia as well as a lower overall level of lighting and visibility.
What is needed is a way to modify all existing incandescent and florescent illuminated exit-type signs in a way that conserves manpower, materials and most of all energy, but has a cost which insures the shortest pay-back periods of the capital investment in the conversion.